BRENDAN TREMBATH: A memorial service in east Texas for the slain district attorney Mike McLelland and his wife Cynthia.

He was a former soldier and his coffin was draped with a US flag. She was a keen quilter, and one of her patchwork quilts was displayed nearby.

One of the mourners was Brandi Fernandez, who will continue Mike McLelland's work as district attorney of Kaufman County. Before the service she spoke of her new role.

BRANDI FERNANDEZ: We take an oath to serve the community and I'll tell you that every prosecutor in this office is stepping up to the plate to uphold that oath and I'm gonna be here beside them and they've all agreed to stay here beside me.

BRENDAN TREMBATH: Mike McLelland and his wife Cynthia were killed in the same county where an assistant district attorney Mark Hasse was shot dead outside a courthouse in January.

Brandi Fernandez could be a target too and has around the clock protection.

BRANDI FERNANDEZ: It certainly puts a kink in your life but I think it's necessary so that we can still show up and get this job done.

BRENDAN TREMBATH: She says not one of them has stayed away from work.

BRANDI FERNANDEZ: On Monday every single person showed up. You know, they're still dedicated to serving this community, they have lots of heart, they're an outstanding team.

BRENDAN TREMBATH: They'll miss Mike McLelland and his wife Cynthia.

BRANDI FERNANDEZ: Mike was our leader of our office. I would just tell you, you know, he was always full of fun, he was always full of life when he came in the office. Him and Cynthia I think were like the mom and the dad of the office. I still kind of keep halfway expecting him to walk through with a plate of cookies that she cooked for us.

BRENDAN TREMBATH: The deaths in Kaufman County are now the subject of a large joint investigation.

The Texas governor Rick Perry has come to the courthouse accompanied by law enforcement officials ranging from Texas rangers to US marshals.

RICK PERRY: Our local, state and federal authorities are pursuing every lead, exhausting every line of inquiry in a relentless pursuit of those who are responsible for these crimes.

BRENDAN TREMBATH: Rick Perry has appealed for anyone with information to come forward.

RICK PERRY: Today I'm announcing that my office is offering a cash reward of up to $100,000 for information leading to the capture and indictment of those responsible for the deaths of Mr and Mrs McLelland as well as Mr Hasse.

RICK PERRY: Texas is a law and order state and we will track down and punish those who have committed this crime.

BRENDAN TREMBATH: He says it's too soon to say who may or may not have been responsible.

RICK PERRY: There was a report by the Department of Public Safety that said the greatest threat to Texan safety were the drug cartels. Obviously that's part of the investigation, those individuals involved with that.

BRENDAN TREMBATH: The Dallas Morning News reports that investigators have also interviewed some members of the Aryan Brotherhood, a white supremacist group with thousands of members in Texas, many of them in jail.

The governor is keeping an open mind.

RICK PERRY: Texas will come together to help track down who these individuals are.

BRENDAN TREMBATH: The interim Kaufman Country district attorney Brandi Fernandez prosecuted a recent abduction case involving the Aryan Brotherhood. The ringleader received a long jail term.